On June 7th of 2023, the Mayon volcano began a new eruption, as lava finally pushed upwards
onto a lava dome emplaced in 2018.
Small sections of this dome were then pushed to too steep of an angle, causing rock fragments
to collapse in rockfall events, with larger events even releasing pyroclastic flows.
It is now day 10 of Mayon's eruption, and volcanic activity is visible over a wide radius
due to an abundance of lava avalanches produced on its slope, where fragments of viscous molten
rock break off from the main lava dome and tumble down Mayon's near 45 degree slopes.
I have attempted to geolocate the lava flow shown in this video clip, which appears to
be occurring on Mayon's southern slope, with fragments of material in the lava flow traveling
up to 1140 meters from Mayon's summit in that direction.
Although lava in of itself can be a deadly hazard, this is not currently the most significant
hazard at the volcano, as that would instead be pyroclastic flows.
These superheated gas currents which regularly produce temperatures beyond 500 degrees Celsius
can incinerate everything in their path and have so far traveled up to a distance of 2600
meters away in the current eruption.
However, there is always the possibility that a larger pyroclastic flow could occur, hence
the current 6 kilometer exclusion zone in all directions around Mayon's summit.
This exclusion zone has resulted in the evacuation of 17,000 people.
And I know those who have evacuated do not want to hear this, but you may be unable to
return to your home for perhaps as long as several months.
Although we no not know how long the current eruption of Mayon will last for, if you look
at Mayon's eruptions since 2000 and exclude brief phreatic eruptions which lasted under
36 hours, the remainder of the eruptions lasted for at least 45 days or more.
Thus, statistics suggest that Mayon will probably still be erupting until at least July 21st,
2023.
In an attempt to determine how explosive Mayon's eruption will be, we will look at its geophysical
data.
Although the number of daily rockfalls at Mayon has largely continued to increase, in
the last 3 days it has remained fairly constant, suggesting a fairly consistent supply of magma
feeding the eruption which is not greatly increasing or decreasing.
The lava which is effusing probably has either a basaltic andesite or andesite composition,
and this is feeding the creation of gas plumes which are remaining under 800 meters in height
above Mayon's summit.
The number of volcanic earthquakes has also remained fairly low since the eruption began,
suggesting that there is not a significant build up in pressure under Mayon's summit
lava dome.
This is a good thing, as it makes powerful explosions that might trigger an expanded
evacuation zone unlikely for now.
However, the most important figure to look at is the amount of sulfur dioxide gas Mayon
is producing.
Generally speaking, the amount of shallow magma present strongly correlates with the
amount of sulfur dioxide which is emitted.
While a baseline or what is considered normal when Mayon is not erupting is under 500 tons
of sulfur dioxide a day, Mayon during the last 7 readings has averaged 620 tons a day.
To understand what exactly this suggests, since Mayon has produced a wide range of eruption
intensities during the last 200 years ranging from fairly peaceful primarily effusive eruption
with negligible if any explosive components to them to highly explosive plinian eruptions,
I present this chart.
As you can see, since the current daily levels of sulfur dioxide emissions are not currently
in the thousands of tons, a highly explosive eruption for now is not expected.
Instead, the current eruption is most consistent with a VEI 0 eruption, although it might be
slightly more gas rich than the 2014 eruption as that eruption averaged under 500 tons sulfur
dioxide emissions a day.
Yet, although Mayon's eruption is seemingly most consisent with a VEI 0 eruption, it could
theoretically be in very weak VEI 1 territory as the volcano has produced 33 pyroclastic
flows between June 7th and June 16th.
In my opinion, I would not be too concerned about the evacuation radius of Mayon expanding
due to an intensifying eruption unless a sudden intense spike in volcanic earthquakes occur
or there are 2 or more days in a row with more than 1,000 tons of sulfur dioxide gas
being produced.
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